From:
Great Circle Mapper Numerous aerodromes don't have identifiers, worldwide. These are just the top 9.
Other Location
GC0001 Groom Lake [Area 51 (Dreamland)], NV, US
GC0002 Vatican City [Heliport], VA
GC0004 Jiuquan Space Launch Facility (Shuang Cheng-Tzu) [LA2], Inner Mongolia, CN
GC0005 Jiuquan Space Launch Facility (Hexixincun) [South Launch Center / LA4], Inner Mongolia, CN
GC0006 Shuangchengzi, Gansu, CN
GC0007 Lamb Holm, Orkney Isles, Scotland, GB
GC0008 Five Mile Tank, Qld, AU
GC0009 Feidong [Feidong AB], Anhui, CN
GC0010 Lanzhou [Lanzhou AB], Gansu, CN